According to this filing with the FCC, Panamsat has requested an extension to operate Galaxy 17 at 123 degrees West until July 9th. It states that additional time is needed to complete in-orbit testing of Galaxy 18 which is occurring now. So it looks like the switch was from Galaxy 10R to Galaxy 17 and another switch will occur within the next month from Galaxy 17 to Galaxy 18.
http://svartifoss2.fcc.gov/servlet/ib.page.FetchAttachment?attachment_key=-148987
http://svartifoss2.fcc.gov/servlet/ib.page.FetchAttachment?attachment_key=-148987